Variable inertia flywheel

ABSTRACT

Variable inertia flywheels are used in power generation apparatus to quickly release stored kinetic energy to meet transient power load demands. Such flywheels typically vary inertia by using either interconnected multiple flywheels having different inertia or by mechanically moving a mass connected with the flywheel radially with respect to the axis of rotation. A variable inertia flywheel according to the present invention comprises a body and a number of fluid movement devices disposed at equal angular intervals about the rotational axis of the body. Each device comprises at least first and second chambers axially aligned in a substantially radial direction and adapted to contain an electrolytic fluid. The first and second chambers are interconnected by a channel that permits transfer of the fluid between the chambers. The movement of the fluid between the chambers is facilitated by an electromagnetic pump.

TECHNICAL FIELD

[0001] The present invention relates to a rotating, kinetic energystorage device, and in particular to a variable inertia flywheelutilizing electromagnetic pumps.

BACKGROUND

[0002] Variable inertia flywheels are utilized in rotating machinery tostore energy that may be quickly released should there be a suddenenergy demand. Such flywheels are common in the field of electricalpower generation. Known variable inertia flywheels vary inertia eitherby interconnecting multiple flywheels having different inertia or bymoving a mass connected with the flywheel radially with respect to theaxis of rotation. The moveable mass can be a solid block or it can alsobe a liquid. One example, where the movement of liquid is facilitated byway of electromechanical pumps can be seen in U.S. Pat. No. 4,735,382.

[0003] However, the more moving parts any apparatus has, the greater thechance of failure during its working life. Additionally, knownmechanical and electromechanical arrangements lack responsiveness whendealing with a sudden increase in demand for power.

[0004] The present invention is directed to overcoming one or more ofthe problems identified above.

SUMMARY OF THE INVENTION

[0005] According to one aspect of the present invention, a variableinertia flywheel comprising a body and a plurality of fluid movementdevices disposed at angular intervals about the axis of rotation of thebody. Each of the devices comprises at least first and second chambersadapted to contain an electrolytic fluid, the chambers being radiallyspaced from each other; and at least one electromagnetic pump for themovement of the fluid between the first and second chambers.

[0006] According to another aspect of the present invention, a method ofvarying the inertia of a flywheel comprising applying an electric fieldto an electrolytic fluid to move said fluid from a first chamberprovided in said flywheel to a second chamber provided in said flywheel,the second chamber being radially spaced from the first chamber.

[0007] In accordance with another aspect of the present invention, amethod of generating electrical power in a power generation apparatuscomprises determining a load demand with a control system, transmittinga demand signal from the control system to a variable inertia flywheel,varying the inertia of the flywheel in response to the demand signal bymoving fluid from a first chamber provided in the flywheel to a secondchamber provided in the flywheel, the first chamber being radiallyspaced from the second chamber, and transferring the stored kineticenergy from the flywheel to the generator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 shows a schematic view of a variable inertia flywheel;

[0009]FIG. 2 shows a view of a portion of the variable inertia flywheelshown in FIG. 1; and

[0010]FIG. 3 shows a schematic diagram of an electrical power generationapparatus incorporating the present invention.

DETAILED DESCRIPTION

[0011] The preferred embodiment described herein shows a rotating,kinetic energy storage device. The energy storage device, or flywheel,may be used with a power generation apparatus. The flywheel useselectromagnetic pumps to move electrolytic fluid between fluid chambersin order to vary the moment of inertia of the flywheel.

[0012] With reference to FIG. 1, there is shown a schematic view of theinternal layout of a variable inertia flywheel 10. The flywheel 10 isformed from a solid disc body 12 in which are located one or more setsof chambers 14,16,18. In the embodiment described herein, the flywheel10 is provided with a pair of fluid movement devices that are locateddiametrically opposite one another on the flywheel 10. Each devicecomprises inner 14, intermediate 16 and outer 18 chambers. The threechambers 14,16,18 are spaced from one another in a radial directionrelative to the axis of rotation 20 of the flywheel 10. Each devicefurther comprises capillary tubes, or channels, 22 of fused silica whichconnect the inner and intermediate chambers 14,16 and the intermediateand outer chambers 16,18. The capillary tubes 22 connect the chambers14,16,18 at openings 14 a, 16 a, 18 a on the radially outermost end ofeach chamber, that is, the ends of the chambers distal the rotationalaxis 20 of the flywheel 10. In the case of the intermediate chamber 16,there are two openings 16 a located at either corner of the chamber 16such that the intermediate chamber 16 communicates with both the innerand outer chambers 14,18.

[0013] As best seen in FIG. 2, each device is provided with anelectromagnetic pump 24, which is a pump for conducting fluid withoutthe use of moving parts. Electromagnetic pumps suitable for this purposehave been developed by Sandia Corporation of California, USA and aredescribed in detail in U.S. Pat. Nos. 6,013,164, 6,019,882, 6,224,728,and 6,277,257.

[0014] The pumps 24 have no moving parts as each uses the principles ofelectro-osmotic flow to move the fluid. Each pump 24 comprises anelectrically energizable coil 26 wrapped around the capillary 22 andconnected to a power supply 30. The power supply 30 includes acommercially available slip ring arrangement to power all the pumps. Apair of spaced-apart electrodes 28 is located inside the capillary andis also connected to the power supply 30. The fluid 32 contained in thechambers 14,16,18 and capillaries 22 is an electrolyte solution (i.e. asolution containing ions and capable of ionic conduction). In theembodiment described here, the fluid 32 is a solution of water andtrisodium phosphate.

[0015] Industrial Applicability

[0016] The present invention varies the inertia of the flywheel 10 bymoving the electrolytic fluid 32 between the chambers 14,16,18. Themanner in which the fluid 32 is moved between the chambers 14,16,18 canbe described best with reference to FIG. 2.

[0017] The specific embodiment described herein relates to a flywheelfor use with a power generation apparatus, as shown in FIG. 3. Theapparatus comprises a control system 40, a generator driving device suchan internal combustion engine 42, a variable inertia flywheel 10 and apower generator 44. The control system 40 has control over both theengine 42 and flywheel 10 via a pair of control inputs 48 a, 48 b. Thecontrol system 40 receives input signals 46 that indicate the presentpower demand and whether a steady state or transient load is requiredfrom the generator 44. If the generation apparatus receives an inputsignal 46 requiring a change from a steady state load to a transientload, it will be necessary to quickly reduce the moment of inertia ofthe flywheel 10, and hence the stored kinetic energy therein, in orderto meet the extra demand. Thus, the control system 40 sends a signal viacontrol input 48 b to the flywheel 10 to reduce the moment of inertiathereof. As the moment of inertia is reduced, the kinetic energy of theflywheel 10 is transferred 50 to the generator 44, allowing thegenerator to increase the amount of power generated through an outlet52.

[0018] Referring again to FIG. 2, to reduce the moment of inertia, theelectrolytic fluid 32 in the flywheel must be pumped towards the axis ofrotation 20 of the flywheel 10. In the embodiment described herein,there are two sets of three chambers 14,16,18 positioned diametricallyopposite one another on the flywheel 10. To reduce the moment of inertiaof the flywheel 10 to a minimum it is necessary to pump the fluid 32into the inner chambers 14 from the intermediate 16 or outer chambers18.

[0019] The method of operation of the pumps 24 between the chambers14,16,18 is the same, whether fluid 32 is being pumped from the outer 18or intermediate 16 chambers. As the openings 14 a,16 a,18 a of thechambers 14,16,18 are located on the outermost edges of the chambers14,16,18, the centrifugal force of the rotating flywheel 10 ensures thatthe fluid 32 will always be in the ideal position within the chamber14,16,18 for pumping. Once the energy demand has been received by acontrol system (not shown), the control system will then send a signalto the pumps 24 of the respective sets of chambers to pump the fluid 32to the inner chamber 14.

[0020] Upon receipt of the signal from the control system, the pumps 24apply an electric potential between the electrodes 28 and anelectromagnetic field in the coil 26 by way of the power supply 30. Theelectrodes 28 are in contact with the electolyte 32 contained within thecapillaries 22. The direction of flow of the electrolyte 32 isdetermined by the polarity of the applied electric potential.Furthermore, the flow rate of the electrolyte 32 is determined by themagnitude of the applied electric potential, where the flow rate willincrease in proportion to an increase in electric potential. Thus, tomove the electrolytic fluid 32 in the opposite direction (i.e. to pumpfrom the inner chamber 14 towards the intermediate 16 and outer chambers18), the polarity of the electric potential applied between theelectrodes and through the coil is simply reversed.

[0021] The present invention enables the inertia of a flywheel to beadjusted by moving a fluid between chambers using hydraulic pumps that,due to the application of electro-osmotic flow properties, require nomoving parts. As there are no moving parts in the pumps, the pumps willnot be susceptible to frictional wear unlike conventional mechanicalfluid movement systems. Furthermore, as the system of fluid movementwithin the flywheel is electrical rather than mechanical, it can berapidly turned on and off to provide a more instantaneous response tosudden energy demands compared with conventional flywheel arrangements.As apparent, the inertia of the flywheel can be varied to transmitstored energy to the generator while maintaining the power output of theinternal combustion engine at a constant level.

[0022] Although the above description is of one particular embodiment ofthe present invention, modifications and improvements can beincorporated without departing from the scope of the invention. Forexample, by varying the number of fluid movement devices on the flywheeland/or the number of chambers in each fluid movement device, the inertiaof the flywheel can be controlled more accurately than existing variableinertia flywheels. Hence, each device could be provided with two, threeor more chambers depending on the operational requirements of theflywheel. The flywheel can also be provided with two or more fluidmovement devices, so long as each device is disposed symmetrically aboutthe axis of rotation of the flywheel to maintain balance. Furthermore,the capillaries may take a number of forms in addition to the silicastructure given as an example herein, while the electrolytic fluid maybe any solution containing ions and being capable of ionic conduction.Although the preferred embodiment of the flywheel has only one slip ringarrangement for powering the pumps, an alternative arrangement may alsobe used. In the alternative arrangement, a slip ring arrangement isprovided for each level of pumps, that is one arrangement for poweringthe pumps between the outer and intermediate chambers and onearrangement for powering the pumps between the intermediate and innerchambers. Those skilled in the art will also recognize that certainaspects of this invention may be implemented with suitable pumps otherthan the electromagnetic pumps described above.

what is claimed is:
 1. A variable inertia flywheel comprising a body anda plurality of fluid movement devices disposed about the axis ofrotation of the body, each of the devices comprising: at least first andsecond chambers adapted to contain an electrolytic fluid, the chambersbeing radially spaced from each other; and at least one electromagneticpump for the movement of the fluid between the first and secondchambers.
 2. The variable inertia flywheel of claim 1, wherein the firstand second chambers are formed within the body.
 3. The variable inertiaflywheel of claim 1, wherein the first and second chambers are axiallyaligned in a substantially radial direction relative to the axis ofrotation.
 4. The variable inertia flywheel of claim 1, wherein eachfluid movement device further comprises at least a first channelpermitting transfer of the fluid between the first and second chambers.5. The variable inertia flywheel of claim 1, wherein the electromagneticpump comprises: an electrically energizable coil disposed about theexterior of the first channel; a pair of electrodes spaced from oneanother and in communication with the electrolytic fluid; and a powersupply for applying an electric potential to the electrodes and thecoil.
 6. The variable inertia flywheel of claim 1, wherein each chamberhas an outer end disposed distal the rotational axis and where itsrespective channel opens into the chamber adjacent the outer end, thechamber being adapted such that the fluid is urged toward the outer endunder the action of centrifugal force.
 7. The variable inertia flywheelof claim 1, wherein each of the devices comprises first, second andthird chambers, and first and second electromagnetic pumps for themovement of fluid between the first and second and second and thirdchambers, respectively.
 8. The variable inertia flywheel of claim 1,wherein the plurality of fluid movement devices are disposed at equalangular intervals about the axis of rotation of the body.
 9. Thevariable inertia flywheel of claim 1, wherein the electrolytic fluid isa solution of water and trisodium phosphate.
 10. A power generationapparatus, comprising: a generator driving device; a variable inertiaflywheel according to claim 1 drivingly connected with the generatordriving device; and a generator drivingly connected with the variableinertia flywheel.
 11. The power generation apparatus of claim 10,further comprising: a control system adapted to determine a load demandand operable to control the inertia of said variable inertia flywheel inresponse to the determined load demand.
 12. The power generationapparatus of claim 10, wherein the generator driving device includes aninternal combustion engine.
 13. A method of varying the inertia of aflywheel comprising applying an electric field to an electrolytic fluidto move said fluid from a first chamber provided in said flywheel to asecond chamber provided in said flywheel, the first chamber beingradially spaced from said second chamber.
 14. A method of generatingelectrical power in a power generation apparatus comprising a controlsystem, a generator driving device, a variable inertia flywheel, and agenerator, the method comprising the steps of: determining a load demandwith the control system; transmitting a demand signal from the controlsystem to the variable inertia flywheel; varying the inertia of theflywheel in response to the demand signal by moving fluid from a firstchamber provided in said flywheel to a second chamber provided in saidflywheel, the first chamber being radially spaced from said secondchamber; and transferring the stored kinetic energy from the flywheel tothe generator.
 15. The method of claim 14 wherein said flywheelcomprises the flywheel of claim 1, wherein the fluid comprises anelectrolytic fluid, and wherein said varying step includes applying anelectric field to the electrolytic fluid to move said fluid from thefirst chamber to the second chamber.
 16. The method of claim 14, furthercomprising: during the varying and transferring step, maintaining apower output of the generator driving device at a substantially constantlevel.